This invention relates to a new and improved heating and cooling apparatus, and more specifically to a heat transfer and storage system utilizing a heat pump and a heat storage system such as a water tank and solar collector.
Generally, a heat pump comprises a compressor, an expansion valve, an indoor heat exchange coil, an outdoor heat exchange coil, a refrigerant fluid, suitable refrigerant pipe line, and a refrigerant flow reversing valve. The heat pump has two sides; a low pressure side and a high pressure side. This pressure difference is caused by the compressor and expansion valve which also separate the two sides. One heat exchanging coil is located on one pressure side while the second coil is on the other side, and generally one coil is located inside an enclosure to be heated or cooled and the other coil is located outdoors. The reversing valve is used to reverse the direction of the flow of refrigerant through the heat pump which has the effect of reversing the pressure sides. Thus, at one time the inside coil can be on the low pressure side while at another time the outside coil can be on the low pressure side. Heat is absorbed by the refrigerant in the coil on the low pressure side and given up by the refrigerant in the coil on the high pressure side.
Thus, a heat pump transfers heat between the indoor and outdoor coil depending on the position of the reversing valve. The heat pump can be used, for example, during cold weather to move heat from the outdoors to an indoor enclosure to warm the enclosure. At times when the outdoor temperature is very low a heat pump cannot transfer enough heat from the outdoors to the enclosure to satisfactorily warm the enclosure and requires supplemental heat such as electrical resistance heating. The system disclosed herein provides supplemental heat from inexpensive heat sources such as solar heat by utilizing a heat storage facility such as an insulated water tank to transfer heat either to the indoors directly or to the heat pump which then transfers the heat indoors. Heat can be put into the heat storage facility from the heat pump when it is convenient and economical to do so or from another heat source such as a solar collector and stored until needed.
In addition to assisting a heat pump in heating an enclosure, a heat storage facility can also be used to assist the heat pump in cooling the enclosure. For example, if the temperature of the heat storage facility is lower than the temperature of the air surrounding the outdoor coil of the heat pump, then the heat pump can operate more efficiently if heat from the outdoor coil, which is the condenser coil when the heat pump is cooling the enclosure, is transferred to the heat storage facility than if the heat is transferred to the relatively warmer ambient air.
The system disclosed utilizes an integrated three medium heat exchanger. A suitable heat exchanger of this type is disclosed in copending application Ser. No. 817,946 filed July 22, 1977 now abandoned in the names of David F. Wilson and Thomas E. Brendel. In a preferred embodiment the three medium heat exchanger is used to effect heat exchange between air, water from the heat storage facility, and refrigerant from the heat pump. An air-water refrigerant heat exchanger, when used with a heat pump, can improve the efficiency of the heat pump in several ways. For example, if the air-water-refrigerant heat exchanger is used in association with the outdoor coil of the heat pump, then when the heat pump is used to heat the enclosure and the outdoor coil functions as the evaporator coil the build up of frost on the evaporator coil can be eliminated. Also, an integrated unit has inherent advantages of low cost, minimum complexity, and compactness which are particularly desirable in systems designed for use in residential homes.